Section 13. qxd

(turning
centers),
are built with the speed capacity, stiffness, and strength capa-
ble of taking full advantage of new and stronger tool materials. The
main drive-motor capacity of lathes ranges from fractional to more than
200 hp (150 kW). Speed preselectors, which give speed as a function of
work diameter, are introduced, and variable-speed drives using dc
motors with panel control are standard on many lathes. Lathes with
contour facing, turning, and boring attachments are also available.
Tool Shapes for Turning
The standard 
nomenclature
for single-point tools, such as those used on
lathes, planers, and shapers, is shown in Fig. 13.4.11. Each tool consists
of a shank and point. The point of a single-point tool may be formed by
grinding on the end of the shank; it may be forged on the end of the
shank and subsequently ground; a tip or insert may be clamped or
brazed to the end of the shank (see Fig. 13.4.8). The 
best tool shape
for
each material and each operation depends on many factors. For specific
information and recommendations, the various sources listed in the
References should be consulted. See also Table 13.4.3.
Fig. 13.4.10
A turning operation on a round workpiece held in a three-jaw
chuck.
Lathes generally are considered to be the oldest member of machine
tools, having been first developed in the late eighteenth century. The most
common lathe is called an engine lathe because it was one of the first
machines driven by Watt’s steam engine. The basic lathe has the follow-
ing main parts: bed, headstock, tailstock, and carriage. The types of lathes
available for a variety of applications may be listed as follows: engine
lathes, bench lathes, horizontal turret lathes, vertical lathes, and
automatics. A great variety of lathes and attachments are available within
each category, also depending on the production rate required.
It is common practice to specify the size of an engine lathe by giving
the